Semiconductor devices and methods for manufacturing the same

ABSTRACT

Semiconductor devices and methods for manufacturing the same are disclosed. In one aspect, the method comprises forming a first shielding layer on a substrate, and forming one of source and drain regions with the first shielding layer as a mask. Then, forming a second shielding layer on the substrate, and forming the other of the source and drain regions with the second shielding layer as a mask. Then, removing a portion of the second shielding layer which is next to the other of the source and drain regions. Lastly, forming a first gate dielectric layer, a floating gate layer, and a second gate dielectric layer, and forming a gate conductor as a spacer on a sidewall of a remaining portion of the second shielding layer.

RELATED APPLICATIONS

This application claims priority to International Application No.PCT/CN2012/085252, filed on Nov. 26, 2012, and Chinese Application No.201210441393.0, entitled “SEMICONDUCTOR DEVICES AND METHODS FORMANUFACTURING THE SAME,” filed on Nov. 7, 2012, which is incorporatedherein by reference in its entirety.

BACKGROUND

1. Field

The disclosed technology relates to the semiconductor field, andparticularly, to semiconductor devices and methods for manufacturing thesame.

2. Description of the Related Technology

With continuous scaling down of semiconductor devices, short channeleffects are becoming more significant. Thus, a gate stack configurationcomprising a high-K gate dielectric and a metal gate conductor isproposed. To avoid degradation of the gate stack, semiconductor deviceswith such a gate stack configuration are manufactured generally by meansof the replacement gate process. The replacement gate process involvesfilling the high-K dielectric and the metal gate conductor in a gapdefined between gate spacers. However, it is becoming more and moredifficult to fill the high-K dielectric and the metal gate conductor inthe small gap due to the scaling down of the semiconductor devices.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The disclosed technology provides, among others, semiconductor devicesand methods for manufacturing the same.

One aspect of the disclosed technology, is a method for manufacturing asemiconductor device, comprising forming a first shielding layer on asubstrate, and forming one of source and drain regions with the firstshielding layer as a mask. Then, forming a second shielding layer on thesubstrate, and forming the other of the source and drain regions withthe second shielding layer as a mask. Then, removing a portion of thesecond shielding layer which is next to the other of the source anddrain regions. Lastly, forming a first gate dielectric layer, a floatinggate layer, and a second gate dielectric layer, and forming a gateconductor as a spacer on a sidewall of a remaining portion of the secondshielding layer.

Another aspect of the disclosed technology, is a semiconductor devicecomprising: a substrate, and source and drain regions and a gate stackformed on the substrate. In some embodiments of the disclosedtechnology, the gate stack comprises a first gate dielectric layer; afloating gate layer; a second gate dielectric layer; and a gateconductor, which is formed as a spacer on a sidewall of a dielectriclayer or a gate spacer on one side of the gate stack.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the disclosedtechnology will become apparent from following descriptions ofembodiments with reference to the attached drawings, in which:

FIGS. 1-9 are schematic views showing a flow of manufacturing asemiconductor device according to an embodiment of the disclosedtechnology;

FIG. 10 is a schematic view showing a semiconductor device according toa further embodiment of the disclosed technology;

FIGS. 11-17 are schematic views showing a flow of manufacturing asemiconductor device according to a further embodiment of the disclosedtechnology;

FIGS. 18-20 are schematic views showing a flow of manufacturing asemiconductor device according to a further embodiment of the disclosedtechnology;

FIG. 21 is a schematic view showing a semiconductor device according toa further embodiment of the disclosed technology; and

FIGS. 22-26 are schematic views showing, in part, a flow ofmanufacturing a semiconductor device according to a further embodimentof the disclosed technology.

FIG. 27 is a flow chart illustrating a method of manufacturing asemiconductor device.

DETAILED DESCRIPTION OF CERTAIN ILLUSTRATIVE EMBODIMENTS

Hereinafter, descriptions are given with reference to embodiments shownin the attached drawings. However, it is to be understood that thesedescriptions are illustrative and not intended to limit the disclosedtechnology. Further, in the following, known structures and technologiesare not described to avoid obscuring the disclosed technologyunnecessarily.

In the drawings, various structures according to the embodiments areschematically shown. However, they are not drawn to scale, and somefeatures may be enlarged while some features may be omitted for sake ofclarity. Moreover, shapes and relative sizes and positions of regionsand layers shown in the drawings are also illustrative, and deviationsmay occur due to manufacture tolerances and technique limitations inpractice. Those skilled in the art can also devise regions/layers ofother different shapes, sizes, and relative positions as desired.

In the context of the disclosed technology, when a layer/element isrecited as being “on” a further layer/element, the layer/element can bedisposed directly on the further layer/element, or otherwise there maybe an intervening layer/element interposed therebetween. Further, if alayer/element is “on” a further layer/element in an orientation, thenthe layer/element can be “under” the further layer/element when theorientation is turned.

In the conventional process, after source and drain regions are formedin a substrate with the aid of a “dummy” gate stack and spacers onopposite sides of the dummy gate stack, the spacers are reserved todefine a gap therebetween, and a true gate stack can be formed byfilling the gap. In contrast, the disclosed technology proposes a“replacement spacer” process. Specifically, after source and drainregions are formed, material layer(s) present on the side of either oneof the source and drain regions is (are) reserved, and a gate stack(particularly, a gate conductor) is formed in the form of spacer on asidewall of the reserved material layer(s). In this way, formation ofthe gate stack is done in a relatively large space (substantiallycorresponding to a gate region+the other of the source and drainregions). This process is easier to perform as compared with theconventional process where formation of the gate stack is done in thesmall gap between the spacers.

According to embodiments of the disclosed technology, the source anddrain regions can be formed in an active region of the substrate bymeans of shielding layer(s). For example, a first shielding layer may beadopted to mask the active region to expose a portion of the activeregion, which can be processed to form one of the source and drainregions. Further, a second shielding layer may be adopted to mask theactive region to expose another portion of the active region, which canbe processed to form the other of the source and drain regions.

The first and second shielding layers can be formed in various ways,provided that they can shield the active region to expose the respectiveportions of the active region. In this way, the first and secondshielding layers serve as masks in the source/drain formation process.Further, the second shielding layer may comprise some portion(s) fromthe first shielding layer.

When the source and drain regions are formed as described above, thesecond shielding layer can be patterned so that a portion thereof isremoved, to further expose a further portion of the active region. Onthe exposed further portion, a gate stack can be formed. For example,the gate stack may be formed by a spacer formation process. Forconvenience of patterning the second shielding layer, the secondshielding layer may preferably comprise several portions of differentmaterials, at least some of which have etching selectivity with respectto each other so that some of them can be removed selectively.

The disclosed technology can be implemented in various ways, some ofwhich will be described in the following by way of example.

Firstly, a flow of manufacturing a semiconductor device according to anembodiment of the disclosed technology is described with reference toFIGS. 1-9.

As shown in FIG. 1, a substrate 100 is provided. The substrate 100 maycomprise any suitable substrate, including, but not limited to, a bulksemiconductor substrate such as a bulk Si substrate, a Semiconductor OnInsulator (SOI) substrate, a SiGe substrate, and the like. In thefollowing, the substrate is described as a bulk Si substrate forconvenience. On the substrate 100, Shallow Trench Isolations (STIs) 102can be formed to isolate active regions of individual devices. Forexample, the STIs 102 may comprise oxide (e.g., silicon oxide). In thefollowing, formation of a single one device is described forconvenience. However, it is to be noted that the disclosed technology isnot limited thereto, and is also applicable to formation of two or moredevices.

Next, as shown in FIG. 2, a thin oxide layer (e.g., silicon oxide) 104is optionally formed on a surface of the substrate 100 by means of e.g.deposition. For example, the oxide layer 104 may have a thickness ofabout 5-10 nm, and can be used to form an Interfacial Layer (IL)subsequently. On the substrate 100 (or on the oxide layer 104 in thecase where the oxide layer 104 is formed), a first shielding sub-layer106 with a thickness of e.g. about 100-200 nm can be formed by means ofe.g. deposition. For example, the first shielding sub-layer 106 maycomprise nitride (e.g. silicon nitride). The first shielding sub-layer106 can be patterned by means of e.g. Reactive Ion Etching (RIE) tocover a portion of the active region (which portion substantiallycorresponds to a later formed source or drain region).

In the case where the oxide layer 104 is formed, the oxide layer 104 canbe selectively etched with respect to the first shielding sub-layer 106(e.g., nitride) and the substrate 100 (e.g., bulk Si), to form an IL 108with a thickness of e.g. about 0.5-1 nm, as shown in FIG. 3. Here, thedifference in thickness between the IL 108 and the oxide layer 104 isnot shown for convenience of illustration.

Further, as shown in FIG. 3, a first spacer 112 may be formed on asidewall of the first shielding sub-layer 106. For example, the firstspacer 112 is formed to have a width of about 15-60 nm to cover aportion of the active region (which portion substantially corresponds toa later formed gate region). The first spacer 112 may comprisepolysilicon or amorphous silicon, for example. There are various ways toform the spacer, and detailed descriptions on formation of the spacerare omitted here.

Thus, the first shielding sub-layer 106 and the first spacer 112 (whichtogether constitute the “first shielding layer” as described above)expose a portion of the active region. Then, one of the source and drainregions can be formed in the exposed portion of the active region bymeans of a source/drain formation process. For example, this can be doneas follows.

Specifically, as shown in FIG. 3 (especially, indicated by verticalarrows shown therein), extension implantation can be carried out to forman extension region 116. For example, for a p-type device, theimplantation can be done by implanting p-type impurities such as In, BF2or B; for a n-type device, the implantation can be done by implantingn-type impurities such as As or P, to form the extension region. It isto be noted that the dashed line block 116 in FIG. 3 is shown as aregular rectangular shape for convenience of illustration. In practice,the profile of the extension region 116 depends on the process, and mayhave no definite boundaries. Further, to improve the performance, haloimplantation can be carried out before the extension implantation, asindicated by angled arrows in FIG. 3. For example, for a p-type device,the implantation can be done by implanting n-type impurities such as Asor P; for a n-type device, the implantation can be done by implantingp-type impurities such as In, BF2 or B, to form a halo region (notshown).

Then, as indicated by arrows in FIG. 4, source/drain implantation can bedone to form a source/drain implantation region 118. For example, for ap-type device, the implantation can be done by implanting p-typeimpurities such as In, BF2 or B; for a n-type device, the implantationcan be done by implanting n-type impurities such as As or P, to form thesource/drain implantation region. It is to be noted that the dashed lineblock 118 in FIG. 4 is shown as a regular rectangular shape forconvenience of illustration. In practice, the profile of thesource/drain implantation region 118 depends on the process, and mayhave no definite boundaries.

Next, as shown in FIG. 5, a second shielding sub-layer 120 may be formedon the substrate 100, to cover at least the above formed one of thesource and drain regions. For example, the second shielding sub-layer120 may comprise oxide (e.g., silicon oxide). Then, a planarizationprocess such as Chemical Mechanical Polishing (CMP) can be performed toexpose the first shielding layer (including the first shieldingsub-layer 106 and the first spacer 112) to facilitate followingprocesses.

Subsequently, as shown in FIG. 6, the first shielding sub-layer 106 canbe removed by selectively etching the first shielding sub-layer 106(e.g., silicon nitride) with respect to the first spacer 112 (e.g.,polysilicon or amorphous silicon), and the second shielding sub-layer120 and the oxide layer 104 (e.g., silicon oxide). The selective etchingcan be done by hot phosphoric acid, for example.

Thus, as shown in FIG. 6, the second shielding sub-layer 120 and thefirst spacer 112 (which together constitute the “second shielding layer”as described above) expose a portion of the active region. Then, theother of the source and drain regions can be formed in the exposedportion of the active region by means of a source/drain formationprocess. For example, this can be done as follows.

Specifically, as shown in FIG. 6, extension implantation can be carriedout to form an extension region 124. For example, for a p-type device,the implantation can be done by implanting p-type impurities such as In,BF2 or B; for a n-type device, the implantation can be done byimplanting n-type impurities such as As or P, to form the extensionregion. It is to be noted that the dashed line block 124 in FIG. 6 isshown as a regular rectangular shape for convenience of illustration. Inpractice, the profile of the extension region 124 depends on theprocess, and may have no definite boundaries. Further, to improve theperformance, halo implantation can be carried out before the extensionimplantation. For example, for a p-type device, the implantation can bedone by implanting n-type impurities such as As or P; for a n-typedevice, the implantation can be done by implanting p-type impuritiessuch as In, BF2 or B, to form a halo region (not shown). After that,source/drain implantation can be done to form a source/drainimplantation region 126. For example, for a p-type device, theimplantation can be done by implanting p-type impurities such as In, BF2or B; for a n-type device, the implantation can be done by implantingn-type impurities such as As or P, to form the source/drain implantationregion. It is to be noted that the dashed line block 126 in FIG. 6 isshown as a regular rectangular shape for convenience of illustration. Inpractice, the profile of the source/drain implantation region 126depends on the process, and may have no definite boundaries.

Next, as shown in FIG. 7, annealing, such as spike annealing, laserannealing, and flash annealing, can be performed to activate theimplanted impurities, to form final source and drain regions 128. Then,the first spacer 112 can be removed by selective etching. For example,the first spacer 112 (e.g., polysilicon or amorphous silicon) may beselectively removed by means of a TMAH solution. As a result, arelatively large space (substantially corresponding to the gateregion+the other of the source and drain regions) is reserved on theside of the second shielding sub-layer 120, so that it is easy to form agate stack.

Then, as shown in FIG. 8, the gate stack can be formed. Specifically, afirst gate dielectric layer 142 can be formed by means of e.g.deposition. For example, the first gate dielectric layer 142 maycomprise a high-K gate dielectric material such as HfO2, with athickness of about 2-4 nm. Optionally, an IL can be rebuilt beforeformation of the first gate dielectric layer 142. For example, the IL(not shown) can be formed by selectively etching the oxide layer 104, asdescribed above with reference to FIG. 3. On the first gate dielectriclayer 142, a floating gate layer 144 and a second gate dielectric layer130 can be formed in sequence by means of e.g. deposition. On the secondgate dielectric layer 130, a gate conductor layer 134 can be formed. Forexample, each of the floating gate layer 144 and the gate conductorlayer 134 may comprise a metal gate conductor material, such as Ti, Co,Ni, Al, W, or any alloy thereof, and the second gate dielectric layer130 may comprise a high-K gate dielectric material such as HfO2, with athickness of about 2-4 nm.

Preferably, there may be a work function adjustment layer 132 sandwichedbetween the second gate dielectric layer 130 and the gate conductorlayer 134. For example, the work function adjustment layer 132 maycomprise any one of TaC, TiN, TaTbN, TaErN, TaYbN, TaSiN, HfSiN, MoSiN,RuTa, NiTa, MoN, TiSiN, TiCN, TaAlC, TiAlN, TaN, PtSi, Ni3Si, Pt, Ru,Ir, Mo, HfRu, RuOx, or any combination thereof, with a thickness ofabout 2-10 nm.

The gate conductor layer 134 can be patterned into a gate conductor inthe form of spacer. For example, parameters adopted in the spacerformation process, such as deposition thickness and RIE parameters, canbe controlled to locate the gate conductor 134 in the form of spacersubstantially between the underlying source and drain regions formed asdescribed above.

After that, the (optional) work function adjustment layer 132, thesecond gate dielectric layer 130, and the floating gate layer 144 can bepatterned, by means of, e.g., RIE, in sequence using the gate conductoras a mask. Optionally, the first gate dielectric layer 142 can be alsopatterned by means of, e.g., RIE.

Here, as shown in FIG. 9, preferably a patterned mask layer 146 (such asphotoresist) may be formed on the gate conductor layer 134 before it ispatterned, to cover a portion of the gate conductor layer 134. In theexample shown in FIG. 9, the portion of the gate conductor layer 134covered by the mask layer 146 extends laterally to cover at leastportions of the (optional) work function adjustment layer 132, thesecond gate dielectric layer 130, and the floating gate layer 144disposed on the sidewall of the second shielding sub-layer 120.

Then, the gate conductor layer 134 may be patterned in accordance withthe spacer formation process. In this way, the resultant gate conductor134 comprises a portion which is disposed on the sidewall of the secondshielding sub-layer 120 in the form of spacer and also a portion whichextends laterally due to the coverage of the mask layer 146.

After that, the (optional) work function adjustment layer 132, thesecond gate dielectric layer 130, and the floating gate layer 144 can bepatterned, by means of, e.g., RIE, in sequence using the resultant gateconductor as a mask. As a result, the laterally extending portion coversthe patterned floating gate layer 144 at least in the lateral direction,so that it is possible to more effectively avoid electrical contactbetween the floating gate layer 144 and contact(s) which may be formedabove the gate stack. Then, the mask layer 146 can be removed.

An interlayer dielectric layer can be formed by means of e.g.deposition, and planarized by means of e.g., CMP. The interlayerdielectric layer may comprise oxide (e.g., silicon oxide), nitride orany combination thereof. Then, peripheral components such as contactscan be formed, and detailed descriptions thereof are omitted here.

Thus, an illustrative semiconductor device according to the disclosedtechnology is achieved. As shown in FIG. 9, the semiconductor device maycomprise the source and drain regions (128) and the gate stack (142,140, 130, 132, 134) formed on the substrate. The gate stack, especially,the gate conductor 134, is formed in the form of spacer on the sidewallof the shielding layer (or, a dielectric layer) 120 on one side (theleft side in the example shown in FIG. 9) of the gate stack.

Because the gate stack includes the floating gate layer 144 therein, thesemiconductor device can be used as a flash memory device. As describedabove, preferably the gate conductor 134 includes the laterallyextending portion which covers the floating gate layer 144 at least inthe lateral direction.

FIG. 10 is a schematic view showing a semiconductor device according toa further embodiment of the disclosed technology. The semiconductordevice shown in FIG. 10 differs from that shown in FIG. 9 in that: thegate stack, especially, the gate conductor 134, is formed in the form ofspacer on a sidewall of a second spacer 114 on one side (the left sidein the example shown in FIG. 10) of the gate stack. Also, in the exampleshown in FIG. 10, the gate conductor comprises a laterally extendingportion.

The device shown in FIG. 10 can be manufactured according to the processdescribed above with reference to FIGS. 1-9. For example, the secondspacer 114 can be additionally formed on the sidewall of the secondshielding sub-layer 120 after the first spacer 112 is removed (referringto the above descriptions in conjunction with FIG. 7). The second spacer114 may comprise nitride (e.g., silicon nitride), with a thickness ofabout 5-20 nm. Alternatively, the second spacer 114 may be formed by thefirst spacer 112 which is partially removed in the process of removingthe first spacer 112 (referring to the above descriptions in conjunctionwith FIG. 7), or may be formed on a sidewall of the first spacer 112(referring to FIG. 4) in which case the second shielding sub-layer 120is formed on a sidewall of the second spacer 114 (referring to FIG. 5).

Next, a flow of manufacturing a semiconductor device according to afurther embodiment of the disclosed technology is described withreference to FIGS. 11-17. Similar or like reference symbols in FIGS.11-17 denote similar or like components as those shown in FIGS. 1-9. Inthe following, descriptions are mainly directed to differences betweenthis embodiment and the above described embodiments.

As shown in FIG. 11, a substrate 1000 is provided. On the substrate1000, STIs 1002 can be formed. Optionally, a thin oxide layer 1004 isformed on a surface of the substrate 1000. For details of the substrate1000 and the oxide layer 1004, reference may be made to the abovedescriptions on the substrate 100 and the oxide layer 104 in conjunctionwith FIGS. 1-2.

On the substrate 1000 (or on the oxide layer 1004 in the case where theoxide layer 1004 is formed), a first shielding sub-layer 1006 with athickness of e.g. about 100-200 nm can be formed by means of e.g.deposition. For example, the first shielding sub-layer 1006 may comprisenitride (e.g. silicon nitride). The first shielding sub-layer 1006 canbe patterned by means of e.g. RIE to cover a portion of the activeregion (which portion substantially corresponds to a later formed sourceor drain region).

According to an embodiment, for better control of short channel effectsand suppression of band-to-band leakage, a Super-Steep-Retrograded Well(SSRW) 1010 can be formed by ion implantation (indicated by arrows) withthe first shielding sub-layer 1006 as a mask, as shown in FIG. 11. Forexample, for a p-type device, the implantation can be done by implantingn-type impurities such as As, P, or Sb; for a n-type device, theimplantation can be done by implanting p-type impurities such as In, BF2or B, to form the SSRW. It is to be noted that the dashed line block1010 in FIG. 11 is shown as a regular rectangular shape for convenienceof illustration. In practice, the profile of the SSRW 1010 depends onthe process, and may have no definite boundaries.

Subsequently, as shown in FIG. 12, a first sub-spacer 1012 may be formedon a sidewall of the first shielding sub-layer 1006. For example, thefirst sub-spacer 1012 is formed to have a width of about 5-50 nm tocover a portion of the active region (which portion substantiallycorresponds to a later formed gate region). The first sub-spacer 1012may comprise polysilicon or amorphous silicon, for example. On asidewall of the first sub-spacer 1012, a second sub-spacer 1014 may beformed. For example, the second sub-spacer 1014 may comprise oxide(e.g., silicon oxide), with a dimension substantially corresponding to agate spacer (e.g., with a width of about 5-20 nm). There are variousways to form the spacers, and detailed descriptions on formation of thespacers are omitted here.

Thus, the first sub-spacer 1012 and the second sub-spacer 1014 (whichtogether constitute a “first spacer”) and the first shielding sub-layer1006 (which together constitute a “first shielding layer”) expose aportion of the active region. Then, one of the source and drain regionscan be formed in the exposed portion of the active region by means of asource/drain formation process. For example, a halo region (not shown),an extension region 1016 and a source/drain implantation region 1018 canbe formed according to the process described above in conjunction withFIGS. 3 and 4. For details of the halo region, the extension region 1016and the source/drain implantation region 1018, reference may be made tothe above descriptions in conjunction with FIGS. 3 and 4.

Next, as shown in FIG. 13, a second shielding sub-layer 1020 may beformed on the substrate, to cover at least the above formed one of thesource and drain regions. For example, the second shielding sub-layer120 may comprise oxide (e.g., silicon oxide). Then, a planarizationprocess such as CMP can be performed to expose the first shieldingsub-layer 1006 and the first spacer (including the first sub-spacer 1012and the second sub-spacer 1014) to facilitate following processes (asdescribed above in conjunction with FIG. 5).

Subsequently, as shown in FIG. 14, the first shielding sub-layer 1006can be removed by selectively etching (as described above in conjunctionwith FIG. 6). Then, a second spacer 1022 can be formed on a sidewall ofthe first sub-spacer 1012. For example, the second spacer 1022 maycomprise nitride (e.g., silicon nitride), with a dimension substantiallycorresponding to a gate spacer (e.g., with a width of about 5-20 nm).

Thus, as shown in FIG. 14, the second shielding sub-layer 120, the firstspacer (including the first sub-spacer 1012 and the second sub-spacer1014), and the second spacer 1022 (which together constitute a “secondshielding layer”) expose a portion of the active region. Then, the otherof the source and drain regions can be formed in the exposed portion ofthe active region by means of a source/drain formation process. Forexample, a halo region (not shown), an extension region 1024 and asource/drain implantation region 1026 can be formed according to theprocess described above in conjunction with FIG. 6. For details of thehalo region, the extension region 1024 and the source/drain implantationregion 1026, reference may be made to the above descriptions inconjunction with FIG. 6.

Next, as shown in FIG. 15, annealing, such as spike annealing, laserannealing, and flash annealing, can be performed to activate theimplanted impurities, to form final source and drain regions 1028.

Subsequently, the second spacer 1022 and a portion of the first spacer(specifically, the first sub-spacer 1012) can be removed by selectiveetching to leave the second sub-spacer 1014 remained. For example, thesecond spacer 1022 (e.g., silicon nitride) may be selectively removed byhot phosphoric acid, and the first sub-spacer 1012 (e.g., polysilicon oramorphous silicon) may be selectively removed by means of a TMAHsolution. As a result, a relatively large space (substantiallycorresponding to the gate region+the other of the source and drainregions) is reserved on the side of the second sub-spacer 1014, so thatit is easy to form a gate stack.

Then, as shown in FIG. 16, the gate stack can be formed. Specifically, afirst gate dielectric layer 1042, a floating gate layer 1044, a secondgate dielectric layer 1030, a work function adjustment layer 1032, and agate conductor 1034 in the form of spacer can be formed sequentially (asdescribed above in conjunction with FIGS. 8 and 9). Preferably, the gateconductor 1034 may comprise a laterally extending portion to cover thefloating gate layer 1044 at least in the lateral direction.

After that, as shown in FIG. 17, an interlayer dielectric layer 1036 canbe formed by means of e.g. deposition, and planarized by means of e.g.,CMP. The interlayer dielectric layer 1036 may comprise oxide (e.g.,silicon oxide), nitride or any combination thereof.

Next, contacts 1040 corresponding to the source and drain regions can beformed. For example, the contacts 1040 may comprise metal such as W orCu. According to an embodiment, to improve the ohmic contact, a metalsilicide layer 1038 may be formed in the source and drain regions, sothat the contacts 1040 are in electrical contact with the source anddrain regions via the metal silicide layer 1038. For example, the metalsilicide layer 1038 may comprise NiPtSi. There are various ways to formthe metal silicide layer 1038 and the contacts 1040, and detaileddescriptions thereof are omitted here.

Thus, an illustrative semiconductor device according to the disclosedtechnology is achieved. As shown in FIG. 17, the semiconductor devicemay comprise the source and drain regions (1028) and the gate stack(1042, 1044, 1030, 1032, 1034) formed on the substrate. On one side (theleft side in the example shown in FIG. 17) of the gate stack, there isthe second sub-spacer 1014. The gate stack, especially, the gateconductor 1034, is formed in the form of spacer on the sidewall of thesecond sub-spacer (or the gate spacer) 1014. Preferably, the gateconductor 1034 may comprise the laterally extending portion to cover thefloating gate layer 1044 at least in the lateral direction. Thesemiconductor device may comprise the asymmetric SSRW 1010, whichextends in the substrate under the gate stack and extends to the sourceor drain region on the one side of the gate stack.

Next, a flow of manufacturing a semiconductor device according to afurther embodiment of the disclosed technology is described withreference to FIGS. 18-20. Similar or like reference symbols in FIGS.18-20 denote similar or like components as those shown in FIGS. 1-10. Inthe following, descriptions are mainly directed to differences betweenthis embodiment and the above described embodiments.

As shown in FIG. 18, a substrate 200 is provided. On the substrate 200,STIs 202 can be formed. Optionally, a thin oxide layer 204 is formed ona surface of the substrate 200. For details of the substrate 200 and theoxide layer 204, reference may be made to the above descriptions on thesubstrate 100 and the oxide layer 104 in conjunction with FIGS. 1-2.

On the substrate 200 (or on the oxide layer 204 in the case where theoxide layer 204 is formed), a first shielding layer 206 with a thicknessof e.g. about 100-200 nm can be formed by means of e.g. deposition. Forexample, the first shielding layer 206 may comprise nitride (e.g.silicon nitride). The first shielding layer 206 can be patterned bymeans of e.g. RIE to expose a portion of the active region (whichportion substantially corresponds to a later formed source or drainregion). Then, one of the source and drain regions can be formed in theexposed portion of the active region by means of a source/drainformation process. For example, a halo region (not shown), an extensionregion 216 and a source/drain implantation region 218 can be formedaccording to the process described above in conjunction with FIGS. 3 and4. For details of the halo region, the extension region 216 and thesource/drain implantation region 218, reference may be made to the abovedescriptions in conjunction with FIGS. 3 and 4.

Next, as shown in FIG. 19, a second shielding sub-layer 220 may beformed on the substrate, to cover at least the above formed one of thesource and drain regions. For example, the second shielding sub-layer220 may comprise oxide (e.g., silicon oxide). Then, a planarizationprocess such as CMP can be performed to expose the first shielding layer206, which then can be removed by selective etching. Then, a firstspacer 212 may be formed on a sidewall of the second shielding sub-layer220. For example, the first spacer 212 may be formed to have a width ofabout 15-60 nm, to cover a portion of the active region (which portionsubstantially corresponds to a later formed gate region). The firstspacer 212 may comprise polysilicon or amorphous silicon, for example.

Thus, the second shielding sub-layer 220 and the first spacer 212 (whichtogether constitute a “second shielding layer”) expose a portion of theactive region. Then, the other of the source and drain regions can beformed in the exposed portion of the active region by means of asource/drain formation process. For example, a halo region (not shown),an extension region 224 and a source/drain implantation region 226 canbe formed according to the process described above in conjunction withFIG. 6. For details of the halo region, the extension region 224 and thesource/drain implantation region 226, reference may be made to the abovedescriptions in conjunction with FIG. 6.

Next, as shown in FIG. 20, annealing, such as spike annealing, laserannealing, and flash annealing, can be performed to activate theimplanted impurities, to form final source and drain regions 228.

Subsequently, the first spacer 212 can be removed by selective etching.For example, the first spacer 212 (e.g., polysilicon or amorphoussilicon) may be selectively removed by means of a TMAH solution. As aresult, a relatively large space (substantially corresponding to thegate region+the other of the source and drain regions) is reserved onthe side of the second shielding sub-layer 220, so that it is easy toform a gate stack. For example, a first gate dielectric layer 242, afloating gate layer 244, a second gate dielectric layer 230, a workfunction adjustment layer 232, and a gate conductor 234 in the form ofspacer can be formed sequentially (as described above in conjunctionwith FIG. 9). Preferably, the gate conductor 234 may comprise alaterally extending portion to cover the floating gate layer 244 atleast in the lateral direction. The device shown in FIG. 20 issubstantially same in structure as the device shown in FIG. 9.

Though the above descriptions in conjunction with the embodiment shownin FIGS. 18-20 do not involve an IL, operations for forming the IL canbe done as described in the above embodiments.

FIG. 21 is a schematic view showing a semiconductor device according toa further embodiment of the disclosed technology. The semiconductordevice shown in FIG. 21 differs from that shown in FIG. 20 in that: thegate stack, especially, the gate conductor 234, is formed in the form ofspacer on a sidewall of a second spacer 214 on one side (the left sidein the example shown in FIG. 21) of the gate stack.

The device shown in FIG. 21 can be manufactured according to the processdescribed above with reference to FIGS. 18-20. For example, the secondspacer 214 can be additionally formed on the sidewall of the secondshielding sub-layer 220 after the first spacer 212 is removed (referringto the above descriptions in conjunction with FIG. 20). The secondspacer 214 may comprise nitride (e.g., silicon nitride), with athickness of about 5-20 nm. Alternatively, the second spacer 214 may beformed by the first shielding layer 206 which is partially removed inthe process of removing the first shielding layer 206 (referring to theabove descriptions in conjunction with FIG. 19), or may be formed on asidewall of the second shielding sub-layer 220 in which case the firstspacer 212 is formed on a sidewall of the second spacer 214 (referringto FIG. 19).

Next, a flow of manufacturing a semiconductor device according to afurther embodiment of the disclosed technology is described withreference to FIGS. 22-26. Similar or like reference symbols in FIGS.22-26 denote similar or like components as those shown in FIGS. 1-10. Inthe following, descriptions are mainly directed to differences betweenthis embodiment and the above described embodiments.

As shown in FIG. 22, a substrate 2000 is provided. On the substrate2000, STIs 2002 can be formed. Optionally, a thin oxide layer 2004 isformed on a surface of the substrate 2000. For details of the substrate2000 and the oxide layer 2004, reference may be made to the abovedescriptions on the substrate 100 and the oxide layer 104 in conjunctionwith FIGS. 1-2.

On the substrate 2000 (or on the oxide layer 2004 in the case where theoxide layer 2004 is formed), a first shielding sub-layer 2006 with athickness of e.g. about 100-200 nm can be formed by means of e.g.deposition. For example, the first shielding sub-layer 2006 may comprisenitride (e.g. silicon nitride). On a sidewall of the first shieldingsub-layer 2006, a first sub-spacer 2014 can be formed. For example, thefirst sub-spacer 2014 may comprise oxide (e.g., silicon oxide), with adimension substantially corresponding to a gate spacer (e.g., with awidth of about 5-20 nm). Thus, the first shielding sub-layer 2006 and afirst sub-spacer 2014 (which together constitute a “first shieldinglayer”) expose a portion of the active region (which portionsubstantially corresponds to a later formed source or drain region).Then, one of the source and drain regions can be formed in the exposedportion of the active region by means of a source/drain formationprocess. For example, a halo region (not shown), an extension region2016 and a source/drain implantation region 2018 can be formed accordingto the process described above in conjunction with FIGS. 3 and 4. Fordetails of the halo region, the extension region 2016 and thesource/drain implantation region 2018, reference may be made to theabove descriptions in conjunction with FIGS. 3 and 4.

Next, as shown in FIG. 23, a second shielding sub-layer 2020 may beformed on the substrate, to cover at least the above formed one of thesource and drain regions. For example, the second shielding sub-layer2020 may comprise oxide (e.g., silicon oxide). Then, a planarizationprocess such as CMP can be performed to expose the first shieldingsub-layer 2006 and the first sub-spacer 2014. The first shieldingsub-layer 2006 can be removed by selective etching.

According to an embodiment, for better control of short channel effectsand suppression of band-to-band leakage, a SSRW 2010 can be formed byion implantation with the second shielding sub-layer 2020 and the firstsub-spacer 2014 as a mask, as shown in FIG. 23. For details of the SSRW2010, reference may be made to the above descriptions in conjunctionwith FIG. 11.

Subsequently, as shown in FIG. 24, a second sub-spacer 2012 may beformed on a sidewall of the first sub-spacer 2014. For example, thesecond sub-spacer 2012 is formed to have a width of about 5-50 nm tocover a portion of the active region (which portion substantiallycorresponds to a later formed gate region). The second sub-spacer 1012may comprise polysilicon or amorphous silicon, for example. On asidewall of the second sub-spacer 2012, a third sub-spacer 2022 may beformed. For example, the third sub-spacer 2022 may comprise nitride(e.g., silicon nitride), with a dimension substantially corresponding toa gate spacer (e.g., with a width of about 5-20 nm). Thus, the secondshielding sub-layer 2020, the first sub-spacer 2014, the secondsub-spacer 2012, and the third sub-spacer 2022 (which togetherconstitute a “second shielding layer”) expose a portion of the activeregion. Then, the other of the source and drain regions can be formed inthe exposed portion of the active region by means of a source/drainformation process. For example, a halo region (not shown), an extensionregion 2024 and a source/drain implantation region 2026 can be formedaccording to the process described above in conjunction with FIG. 6. Fordetails of the halo region, the extension region 2024 and thesource/drain implantation region 2026, reference may be made to theabove descriptions in conjunction with FIG. 6.

Next, as shown in FIG. 25, annealing, such as spike annealing, laserannealing, and flash annealing, can be performed to activate theimplanted impurities, to form final source and drain regions 2028.

Subsequently, the second sub-spacer 2012 and the third sub-spacer 2022can be removed by selective etching to leave the first sub-spacer 2014remained. For example, the second sub-spacer 2012 (e.g., polysilicon oramorphous silicon) may be selectively removed by means of a TMAHsolution, and the third sub-spacer 2022 (e.g., silicon nitride) may beselectively removed by hot phosphoric acid. As a result, a relativelylarge space (substantially corresponding to the gate region+the other ofthe source and drain regions) is reserved on the side of the firstsub-spacer 2014, so that it is easy to form a gate stack.

The flow can continue similarly to that shown in FIG. 16, and detaileddescriptions thereof are omitted here. For example, the gate stack(including a first gate dielectric layer 2042, a floating gate layer2044, a second gate dielectric layer 2030, a work function adjustmentlayer 2032, and a gate conductor 2034 in the form of spacer) can beformed. Preferably, the gate conductor 2034 may comprise a laterallyextending portion to cover the floating gate layer 2044 at least in thelateral direction. The resultant device is similar to that shown in FIG.16, except that the SSRW 2010 extends to the opposite side.

Though the above descriptions in conjunction with the embodiment shownin FIGS. 22-26 do not involve an IL, operations for forming the IL canbe done as described in the above embodiments.

Manufacturing the semiconductor device shown in FIG. 10 and/or FIG. 21will now be described with respect to FIG. 27, which is a flow chartillustrating a method of manufacturing the semiconductor device. Block2710 of the manufacturing process forms a first shielding layer on asubstrate, and forms one of source and drain regions with the firstshielding layer as a mask. Block 2720 of the manufacturing process formsa second shielding layer on the substrate, and forms the other of thesource and drain regions with the second shielding layer as a mask.Block 2730 of the manufacturing process removes a portion of the secondshielding layer which is next to the other of the source and drainregions. Block 2740 of the manufacturing process forms a first gatedielectric layer, a floating gate layer, and a second gate dielectriclayer, and forms a gate conductor as a spacer on a sidewall of aremaining portion of the second shielding layer.

In the above descriptions, details of patterning and etching of thelayers are not described. It is to be understood by those skilled in theart that various measures may be utilized to form the layers and regionsin desired shapes. Further, to achieve the same feature, those skilledin the art can devise processes not entirely the same as those describedabove. The mere fact that the various embodiments are describedseparately does not mean that means recited in the respectiveembodiments cannot be used in combination to advantage.

From the foregoing, it will be appreciated that specific embodiments ofthe disclosure have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. In addition, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the technology is notlimited except as by the appended claims.

What is claimed is:
 1. A method of manufacturing a semiconductor device,comprising: forming a first shielding layer on a substrate, and formingone of source and drain regions with the first shielding layer as amask; forming a second shielding layer on the substrate, and forming theother of the source and drain regions with the second shielding layer asa mask; removing a portion of the second shielding layer which is nextto the other of the source and drain regions; and forming a first gatedielectric layer, a floating gate layer, and a second gate dielectriclayer, and forming a gate conductor as a spacer on a sidewall of aremaining portion of the second shielding layer.
 2. The method accordingto claim 1, wherein forming the first shielding layer comprises forminga first shielding sub-layer on the substrate and forming a first spaceron a sidewall of the first shielding sub-layer, wherein forming thesecond shielding layer comprises forming a second shielding sub-layer onthe substrate, and removing the first shielding sub-layer, wherein thesecond shielding sub-layer and the first spacer together constitute thesecond shielding layer, wherein removing the portion of the secondshielding layer comprises removing at least a portion of the firstspacer.
 3. The method according to claim 2, wherein forming the firstspacer comprises forming a first sub-spacer on the sidewall of the firstshielding sub-layer and forming a second sub-spacer on a sidewall of thefirst sub-spacer.
 4. The method according to claim 3, wherein formingthe second shielding layer further comprises forming a second spacer ona sidewall of the first spacer such that the first spacer is locatedbetween the second spacer and the second shielding sub-layer, whereinthe second shielding sub-layer, the first spacer, and the second spacertogether constitute the second shielding layer.
 5. The method accordingto claim 4, wherein removing the portion of the second shielding layercomprises removing the second spacer and the first sub-spacer.
 6. Themethod according to claim 4, wherein the first shielding sub-layercomprises nitride, wherein the second shielding sub-layer comprisesoxide, wherein the first sub-spacer comprises polysilicon or amorphoussilicon, wherein the second sub-spacer comprises oxide, wherein thesecond spacer comprises nitride.
 7. The method according to claim 2,further comprising forming a super-steep-retrograded well in thesubstrate with the first shielding sub-layer as a mask.
 8. The methodaccording to claim 1, wherein forming the second shielding layercomprises forming a second shielding sub-layer on the substrate, andremoving at least a portion of the first shielding layer and forming afirst spacer on a sidewall of the second shielding sub-layer or asidewall of a possible remaining portion of the first shielding layer,wherein the second shielding sub-layer, the possible remaining portionof the first shielding layer, and the first spacer together constitutethe second shielding layer, wherein removing the portion of the secondshielding layer comprises removing the first spacer.
 9. The methodaccording to claim 8, wherein forming the first shielding layercomprises forming a first shielding sub-layer and forming a firstsub-spacer on a sidewall of the first shielding sub-layer, whereinremoving the at least portion of the first shielding layer comprisesremoving the first shielding sub-layer.
 10. The method according toclaim 9, wherein forming the first spacer comprises forming a secondsub-spacer on a sidewall of the first sub-spacer and forming a thirdsub-spacer on a sidewall of the second sub-spacer.
 11. The methodaccording to claim 10, wherein the first shielding sub-layer comprisesnitride, wherein the second shielding sub-layer comprises oxide, whereinthe first sub-spacer comprises oxide, wherein the second sub-spacercomprises polysilicon or amorphous silicon, wherein the third sub-spacercomprises nitride.
 12. The method according to claim 9, furthercomprising forming a super-steep-retrograded well in the substrate withthe second shielding sub-layer and the first sub-spacer as a mask. 13.The method according to claim 1, wherein forming the gate conductorcomprises forming a gate conductor layer, forming a patterned mask layeron the gate conductor layer to cover at least a portion of the gateconductor layer, and patterning the gate conductor layer into the gateconductor, wherein the method further comprises patterning at least thesecond gate dielectric layer and the floating gate layer with the gateconductor as a mask, wherein the portion of the gate conductor layercovered by the mask layer constitutes a laterally extending portion ofthe gate conductor, which covers the patterned floating gate layer atleast in a lateral direction.
 14. The method according to claim 1,wherein forming the source or drain region comprises performingextension implantation and performing source/drain implantation.
 15. Themethod according to claim 14, wherein forming the source or drain regionfurther comprises performing halo implantation.
 16. A semiconductordevice, comprising: a substrate; and source and drain regions and a gatestack formed on the substrate, wherein the gate stack comprises a firstgate dielectric layer, a floating gate layer, a second gate dielectriclayer, and a gate conductor formed as a spacer on a sidewall of adielectric layer or a gate spacer on one side of the gate stack.
 17. Thesemiconductor device according to claim 16, wherein each of the firstand second gate dielectric layers comprise a high-K dielectric material,and each of the floating gate layer and the gate conductor comprise ametal gate conductor material.
 18. The semiconductor device according toclaim 16, further comprising a work function adjustment layer disposedbetween the second gate dielectric layer and the gate conductor.
 19. Thesemiconductor device according to claim 18, wherein the work functionadjustment layer comprises any one of TaC, TiN, TaTbN, TaErN, TaYbN,TaSiN, HfSiN, MoSiN, RuTa, NiTa, MoN, TiSiN, TiCN, TaAlC, TiAlN, TaN,PtSi, Ni3Si, Pt, Ru, Ir, Mo, HfRu, RuOx, or any combination thereof. 20.The semiconductor device according to claim 16, further comprising asuper-steep-retrograded well formed in the substrate, which extends toeither the source side or the drain side.
 21. The semiconductor deviceaccording to claim 16, wherein the gate conductor further comprises alaterally extending portion which covers the floating gate layer atleast in a lateral direction.